1. Field of the Invention
This invention relates broadly to medical instruments. More particularly, this invention relates to a releasable catch, stop, and marker assembly for medical instruments.
2. State of the Art
A variety of medical instruments utilize a configuration in which a shaft member is moved relative to and within a tube. For example, in an endoscopic or intravascular basket device, a shaft having a basket at a distal end thereof is moved within a tube to cause the basket to move between open and closed positions. The relative position of the shaft and the tube is adjusted or maintained by the physician operating the instrument. Yet, the shaft and tube may nevertheless be inadvertently moved relative to each other due to physician error or fatigue. In such instruments it is desirable to be able to automatically maintain the relative positions of the shaft and the tube without relying on the physician. It is also desirable for the relative positions of the shaft and the tube to be easily adjustable.
In other instruments, such as biopsy needle and Veress needles for injection into, e.g., the breast, the liver or the brain, it is desirable to use a stop which sets a maximum depth for the needle such that the needle can be safely inserted to a particular depth and no further. Likewise, it is desirable that a stop be easily adjustable such that the needle is permitted less penetration depth, but be adapted to prevent inadvertent movement in a direction which could cause too much penetration.
On yet other medical devices, for example, a guidewire, it is desirable to have an adjustable marker which indicates a reference depth. As such, the relative position of the tip of the device during a procedure can be determined.
It is therefore an object of the invention to provide an assembly which can function as a releasable catch, an adjustable stop, or an adjustable marker on a medical device.
It is another object of the invention to provide an assembly which is easily adjustable.
It is a further object of the invention to provide an assembly which is not prone to failure.
It is an additional object of the invention to provide a mechanism which is easy and inexpensive to manufacture.
In accord with these objects, which will be discussed in detail below, an assembly which functions as a catch, stop, or marker, depending on the device on which it is used, is provided. According to a first embodiment of the invention, the assembly includes a tube having an inner surface, a helically wound coil within the tube, and a shaft extending through the coil and which is lockable in longitudinal position relative to the tube. The shaft may be a portion of a shaft of an endoscopic or intravascular instrument, hypodermic tubing of a needle device, a guidewire, etc. The coil has an outer surface coupled to the tube, and an inner surface interfering with the an outer surface of the shaft such that the coil grips the shaft.
In use, the shaft and tube may be slid relative to each other in a first longitudinal direction, but are substantially prevented from sliding relative to each other in an opposite second longitudinal direction. When it is desired to move the tube relative to the shaft in the second longitudinal direction, the tube is rotated relative to the shaft in a first rotational direction (opposite the direction of the winding of the coil) which causes partial unwinding of the coil to at least reduce the interference between the coil and shaft. As such, rotation of the tube in the first rotational direction in combination with longitudinal movement in the second longitudinal direction moves the tube and coil relative to the shaft. Releasing the rotational force on the tube allows the coil to wind back about the shaft and grip and lock the shaft. Rotation of the tube relative to the shaft in the direction of the winding of the coil causes the coil to grip the shaft tighter and substantially prevents any longitudinal movement of the tube and coil relative to the shaft.
According to a second embodiment of the invention, the assembly includes a tube which is rolled partially closed at a first end, and a sleeve within the tube and having an outer diameter substantially the same size or slightly smaller in size than an inner diameter of the tube. The rolling at the first end of the tube operates to retain the sleeve within the first end of the tube. First and second open pitch helically wound coils in a double-helix arrangement are each attached at one end to the sleeve. A shaft extends through the first and second coils, the sleeve, and the tube. The first coil has a first outer surface which interferes with the inner diameter of the tube. The second coil is more tightly wound than the first coil and has an inner surface which interferes with the outer surface of the shaft such that the second coil grips the shaft.
In use, the tube may be slid relative to the shaft in the first longitudinal direction (the direction in which the first and second coils are axially compressible), but is substantially prevented from being slid along the shaft in an opposite second longitudinal direction. Rotation of the tube relative to the shaft in a first rotational direction opposite the direction of the winding of the coils causes partial unwinding of the coils, and the first coil further interfering with the inner surface of the tube. As such, rotation in the direction opposite the coil winding in combination with longitudinal force on the tube relative to the shaft permits the tube and coil to be moved longitudinally along the shaft. Releasing the rotational force on the tube allows the second coil to wind back about the shaft and grip the shaft at a new location. Rotation of the tube relative to the shaft in the direction of the winding of the coils causes the second coil to grip the shaft tighter and prevents any longitudinal movement of the tube and coil relative to the shaft, and also causes the first coil to decrease in diameter such that the first coil and the sleeve rotatably slip within the tube. As such, the second embodiment of the assembly eliminates the potential present in the first embodiment for fixation failure at the coupling of the coil to the tube when the tube is forcibly rotated in the second rotational direction relative to the shaft. In the second embodiment, such force simply causes slippage of the sleeve relative to the tube.
According to a third embodiment, the assembly includes a tube having an inner surface, a generally uniform diameter helically wound coil within the tube, and a shaft extending through the coil. A portion of the coil is attached to the shaft such that the coil and shaft are coupled together.
In use, forcing the tube relative to the shaft in a first longitudinal direction axially compresses the coil and results in an increased diameter of the coil which substantially prevents the shaft and coil from movement with the tube. Forcing the tube relative to the shaft in an opposite second longitudinal direction operates to axially extend the coil within the tube such that its diameter is reduced and movement of the shaft and coil relative to the tube is facilitated. When it is desired to move the tube relative to the shaft in the first longitudinal direction, the tube is rotated relative to the shaft in the direction of the winding of the coil, which causes radial compression of the coil thereby permitting the coil and shaft to slide within the tube.
It will be appreciated that where the shaft is a portion of the shaft of a medical instrument, e.g. a laparoscopic, endoscopic, or intravascular instrument, the embodiments of the assembly of the invention permit locking the shaft in a position relative to a tube through which the shaft extends. In addition, the shaft may be a medical instrument requiring an easily and quickly adjustable stop along a length of a shaft, e.g., a needle. As such, the assembly may be positioned along a length of the needle to prevent penetration beyond the stop. Adjustment of the stop in a xe2x80x98safexe2x80x99 direction (e.g., in a direction which would further limit penetration of the needle into the human body) can be made by simply sliding the stop along the shaft. Adjustment in a xe2x80x98stoppedxe2x80x99 direction (e.g., in a direction which would permit greater needle penetration) is possible by applying rotational force to the tube relative to the shaft such that the coil about the shaft is partially unwound, moving the tube along the shaft, and then releasing the rotational force to engage the tube about the shaft. Likewise, the assembly can be used as an adjustable marker on a guidewire or similar device to indicate the length of the portion of the guidewire is inserted into a body.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.